Solution: Human blood contains one buffer system based on phosphate species and one based on carbonate species. Assuming that blood has a normal pH of 7.4, what are the principal phosphate and carbonate species present? What is the ratio of the two phosphate species? (In the presence of the dissolved ions and other species in blood, Ka1 of H3PO4 = 1.3 × 10−2, Ka2 = 2.3 × 10−7, and Ka3 = 6 × 10−12; Ka1 of H2CO3 = 8 × 10−7 and Ka2 = 1.6 × 10−10.)

Problem

Human blood contains one buffer system based on phosphate species and one based on carbonate species. Assuming that blood has a normal pH of 7.4, what are the principal phosphate and carbonate species present? What is the ratio of the two phosphate species? (In the presence of the dissolved ions and other species in blood, Ka1 of H3PO4 = 1.3 × 10−2, Ka2 = 2.3 × 10−7, and Ka3 = 6 × 10−12; Ka1 of H2CO3 = 8 × 10−7 and Ka2 = 1.6 × 10−10.)